1: a massive wall used to hold back water, such as those used in Holland to reclaim farmland.
2: an igneous intrusion cutting through layers of older rocks.
3: alternate spelling of 'dyke', referring to a woman whose sexual preference is exclusively other women. See also 'lesbian'.

'I learned about the dikes they use in the Netherlands to keep the ocean from making a seafloor out of their farmlands.'

In electronics, short for diagonal cutters. Used, though, for any small wire-cutting and metal snipping tool. Also, used as a transitive verb for removing something by cutting it out. May also be spelled dyke.